System of temperature control



Nov. 2, 1937. J. G. BEARD 2,097,868

SYSTEM OF TEMPERATURE CONTROL Filed 001'.- 2, 1934 Hernamrwrzc can r404 INVENTOR Joseph G. Beard.

ATTORNE Patented Nov. 2, 1937 UNITED STATES PATENT OFFICE SYSTEM OF TEMPERATURE CONTROL Pennsylvania Application October 2,

9 Claims.

My invention relates to a method and means for stabilizing the operation of radio apparatus or apparatus of similar character, and more particularly to maintaining the frequency of such apparatus free from the influence of changes in load or ambient temperature.

It is a primary object of my invention to obtain a high degree of stabilization of the frequency of apparatus embodying radio circuits or the like.

It is another object of my invention to provide means whereby apparatus may be maintained in operation under constant and uniform temperature conditions.

Another object of my invention resides in the method for maintaining the frequency of radio apparatus constant during operation.

Another object of my invention resides in means as well as the method for bringing radio apparatus up to its desired frequency within a very short period of time.

Another object of my invention is to shorten the period formerly required in bringing radio apparatus up to its operating condition.

Additional objects of my invention will be disclosed in the following description of the same taken in conjunction with the accompanying drawing wherein I have disclosed two embodiments of my invention.

Figure 1 is an illustration of one form of my invention, the greater portion of which is shown in cross-section to enable a disclosure of the details of construction and the manner of operation.

Fig. 2 is a view taken along the line II--II of Fig. 1, and illustrates a feature of the embodiment of Fig. 1, as will be pointed out more particularly in my description of the same.

Fig. 3. is a view of the second form of my invention shown for the most part in crosssection to depict the details of construction and method of operation.

In Fig. 4 I have shown in detail an important feature of construction of Fig. 3, and in Fig. 5 I have illustrated a detail of one of the elements of Fig. 4.

Broadly speaking, my invention comprises subjecting the apparatus to be controlled or a portion thereof to a flow of a fluid medium such as air or other gases, or any suitable liquid and regulating the calorific content of this medium in accordance with heat changes or temperature changes taking place therein, which changes might be attributed to the heat generated within and by the apparatus to be controlled and/or to changes in ambient temperature.

1934, Serial No. 746,519

The fluid medium may either be heated or refrigerated, but in either case the initial temperature should be beyond the limits which are apt to be reached by ambient temperature; If a refrigerant is employed, its temperature should be lower than the temperature which ambient temperature is apt to reach, and if the fluid is to be initially heated, its temperature should be preferably higher than that which is likely to be reached by ambient. In the apparatus as disclosed by me in my drawing, I have illustrated my invention as utilizing an initially heated fluid medium.

The construction shown in Fig. 1 as constituting one embodiment of my invention comprising a thermal chamber i in which is housed the apparatus which is to be controlled or regulated. The apparatus to be controlled may constitute portions of a radio circuit or a complete radio circuit, depending on the type of apparatus and its characteristics. The apparatus which I have shown for purposes of illustration constitutes the tank circuit of an oscillator, the tank circuit including the frequency determining circuit coil 3, its associated turning plunger 5, a shunting condenser and various ancillary elements, it being unnecessary to an understanding of my invention to refer to all of these elements specifically, since they are intended to represent any apparatus in general. It is desired to point out, however, that my apparatus is particularly efiicient in that it responds not only to changes in ambient conditions, but is so designed as to very readily compensate for disturbing conditions which would normally be caused by the generation of heat in the apparatus to be controlled during its normal course of operation.

The thermal chamber has a perforated bottom wall I and is provided with a tapering upper wall or roof 9, the apex of which is open to provide for a flexible connection II to a motor driven fan or blower l3, the casing enclosing the blower being also provided with an opening for connection to an air duct I 5 which may be formed independently of the thermal chamber or integral therewith and comprise a part thereof as shown. This duct extends from the blower down alongside one wall of the thermal chamber and around under the bottom thereof to complete a closed circulating path for air or other fluid medium from the duct through the perforations in the bottom wall of the chamber, through the thermal chamber back to the blower from which the stream of fluid medium originated.

A flexible connection I! is preferably employed between the blower l3 and the air duct I 5 in addi tion to the flexible connection I i between the 'blower and the thermal housing, the purpose of these flexible connections or couplings being to prevent the vibration of the blower or motor from being transmitted to the apparatus within the hermal chamber.

The bottom portion of the air duct I5 is provided with a plurality of baffles l9 extending in the direction of flow. do not impede the flow of the fluid medium, do prevent swirling or the production of circulating currents of the fluid medium within this portion of the duct itself. Thus a continuous and uniform flow of the fluid medium is assured, and through the use of the perforated bottom wall 1 of the thermal chamber, the fluid medium is uniformly transmitted through the thermal. chamber and all parts of the apparatus to be controlled are uniformly exposed to the flow of this medium, the perforations in the bottom wall 1 being so disposed as to create a flow through the chamber of substantially uniform cross-sectional density.

In order to. initially heat the medium to a temperature above that which is likely to be reached by the atmosphere surrounding the chamber, there is located within the air duct, a heater ofany suitable type, preferably an electrical heating element 2!. This heater is connected'to a source of electrical energy, not shown, through the contactsof a thermostat 23 located at the exit of the thermal chamber. The thermostat is encased within an insulating covering or box'to avoid the effects of ambient temperature thereon, and extends through an opening at the upper end of the thermal chamber into the stream of the fluid medium, where it will be subjected to the temperature thereof. By reason of the fact that the roof of the chamber is of tapered construction, the fluid medium after passing the apparatus to be controlled is caused to be concentrated and the thermostat is thereby exposed to the temperature of the concentrated medium. Thus, should the temperature of the medium tend to change due to either the development of heat within the ap paratus to be controlled or to a change in ambient temperature, which change will merely have the eifect of tending to change the temperature of the apparatusto be controlled, the thermostat will respond to such tendencies toward changes in the temperature and will open or close the circuit to the heater in accordance with such changesthus altering the heat content. or calorific content of the fluid medium prior to its entrance into the thermal chamber. The changes in the heat content thus produced will be in such a direction as to compensate for Whatever conditions tend to unbalance the heat conditions within the thermal chamber.

The fluid medium is caused to flow at a rather high velocity and thereby not only exposes the apparatus to be controlled to an exceedingly large volume of temperature regulating medium, but also causes a very rapid response of thethermostat for very small changes. in temperature or heat conditions. The time lag between the cause and effect normally existing in heat controlled apparatus of the prior art does not, exist in the apparatus disclosed by me due to the high velocity at which the fluid medium is caused to travel.

The thermal chamber may be constructed of insulating material as in other systems of the prior art. I have found, however, that contrary These bailies, while they to the teachings of the prior art which stress or emphasize the high insulation factor'necessary in the construction and design of heat chambers, my invention functions very satisfactorily with. a chamber of a good heat conducting material such as metal and when constructed of such material, it possesses in addition, decided advantages over a heat insulated chamber. The same may be more easily and conveniently fabricated such as by castin and being of metal, it will have high thermal conductivity. This characteristic is very desirable in apparatus of the type described, since it will prevent the devolpment of hot or cold spots around the chamber walls, which would tend to be produced due tothe proximity of other apparatus at different" temperatures. Even the fact that the' air duct is built integral with the walls of the thermal chamber would have a tendency to develop a hot wall at this side of the chamber were the chamber constructed of insulating material. When'made of heavy metal, however, the heat is quickly dissipated throughout the walls of the heat chamber, thus creating a substantially uniform condition.

A metallic chamber possesses the further desirable characteristic of being exceedingly rigid, thus permitting a rigid assemblage within the chamber of the apparatus which is to be controlled, since the chamber walls permit of solidly anchoring such apparatus. This is quite desirable since the apparatus, being as it is exposed to the flow of the fluid medium therethrough, is apt to be influenced into vibration were no means provided for rigidly anchoring such apparatus.

The apparatus just described operates by reason of the intermittent operation of the thermostat, which either closes or opens the heater circuit. The operation of this element, however, due to the rapid flow of the fluid medium and due to its own sensitivity is very fast. This coupled With the fact that, the heater normally has comparatively high lagging characteristics, will for all practical purposes, oiier a compensating actionwhich is smoothin character and not intermittent in accordance with the operation of the thermostat.

In the embodiment of my invention as disclosed in Fig. 3, the operation thereof does not depend upon the intermittent opening or closing of the heater circuit. In fact in this modification, the heater is on all the time. The apparatus of this embodiment operates upon the principle of dividing the fluid medium into two streams prior to its entering the thermal chamber, one stream being caused to pass within the influence of a heater located in one of two branch ducts and the other stream being caused to pass through the other duct which contains no heater. By varying the relative amounts of the medium passing into these branch ducts in accordance with heat changes tending to take place in the thermal chamber, one is able to obtain a very gradual and fine control in the amount of heat being added to the fluid medium prior to its entrance into the thermal chamber.

Referring to the drawing, this embodiment comprises a thermal chamber 25 somewhat of the same type as that disclosed in connection with the structure of Fig. l in that it is preferably constructed of metal and is provided with a perforated bottom wall 2'! connecting with an air duct 29. The fluid medium is set in motion by a motor driven blower 3| which causes the medium to pass through a temperature controlled damper element 33 into two branch ducts 35 and 31 which lead into the thermal chamber. In one of these ducts is located a heater 39 which is continually in circuit and adapted to heat that portion of the fluid medium which passes through that particular duct. A perforated wall 4| in the upper portion of the thermal chamber creates a compartment between this Wall and the roof wherein the inflowing medium from both ducts will become thoroughly mixed and uniformly distributed to the apparatus under control through the various perforations. Bafiles of the character of those of Fig. 1 may be employed to reduce or prevent eddying of the medium at this point.

In lieu of having the branch ducts entering the housing individually, they may be terminated in a single duct which enters the thermal chamber from the top. With this construction,

the medium from both branch ducts will be thoroughly mixed in the terminating duct.

An important feature of the construction illustrated in Fig. 3 resides in the means for determining the relative amount of the fluid medium which is to enter the respective ducts. In Fig. 4 I have shown the constructional details of this feature in greater detail. It comprises a plurality of convex discs 4|. These discs may be fastened together by means of elements 43 adapted to join the apex of one disc with the circumference of the adjacent disc, these elements being openly constructed to permit of the free flow of the fluid medium therethrough. The stacked discs are supported within a cage constructed of rods 45 to prevent the stack from twisting or distorting during operation. The discs are formed of high expansion of bimetallic material and in response to temperature changes will either tend to flatten out, or become convex to a greater degree. The displacement of each disc will be added to that of the others, producing a total displacement equal to the sum of the individual displacements of each disc. Therefore, should the heat change be in such a direction as to cause the discs to flatten out, the total displacement will be in one direction, whereas if the discs are caused to convex to a greater degree, the total displacement will be in the opposite direction, the supporting cage being of such dimensions to permit free sliding movement of these discs.

The uppermost disc of the stack is connected to the short end of a lever 41, the long end of which terminates in a somewhat conical shaped damper element 49. This damper element is of a conical shape to prevent fluttering thereof due to the flow of the fluid medium past it and is of such dimensions as to substantially close the opening to either one of the branch ducts when the lever is swung to one or the other of its extreme positions. By crinkling the discs as shown, a greater temperature effect may be obtained, thereby permitting a reduction in the number of the discs which might ordinarily be required.

In the operation of the apparatus as illustrated in Fig. 3 a stream of air or other fluid medium is set up by the motor driven blower and is caused to pass over the stacked temperature responsive discs. A portion of the fluid medium passes through the duct containing the heater and a portion passes through the duct without the heater, both of these. branch ducts discharging into the thermal chamber at one end thereof, the fluid medium being thoroughly mixed prior to passing over the apparatus to be controlled} Should the heat content of this medium be altered in its passage over the apparatus to be controlled, either due to heat generated within the apparatus itself or due to changes in ambient temperature, the fluid medium thus altered will quickly effect the temperature responsive discs causing them either to expand or contract depending on whether heat has been added to or subtracted from the fluid medium. In this way the damper will be caused to move to one side or the other and alter the relative amounts of the medium which pass through the branch ducts. Thus a temperature or heat compensating effect is obtained and the apparatus will be maintained at a constant temperature with the result that the frequency thereof will remain steady and constant.

The housing is provided with eye bolts 5| for suspension from spring supports to preserve the apparatus from external vibrational influences.

My invention is subject to many modifications and alterations without departing from the scope thereof. I accordingly do not desire to be limited in my protection to the specific details shown except as may be necessitated by the prior art and the appended claims.

I claim as my invention:

1. In combination, an oscillation generator comprising a tunable resonant frequency determining circuit, a chamber having walls of material having heat-conductivity of the order of the metals enclosing said frequency determining circuit, means for producing a flow of a fluid medium through said chamber and in physical contact with said frequency determining circuit and said walls, means for varying the heat content of said fluid in accordance with heat changes within said chamber tending to alter the frequency of said generator.

2. In combination, an electron discharge device and connected circuits, said circuits including a tunable resonant circuit adjusted to a definite frequency, a chamber having walls of material having heat-conductivity of the order of the metals enclosing said resonant circuit, means for producing a relatively rapid flow of a fluid medium through said chamber and in physical contact with said resonant circuit and said walls and means responsive to the heat produced in said resonant circuit positioned in said flow immediconveyance of a temperature regulating medium,

said principal duct terminating in at least two branch ducts, means for distributing said temperature regulating medium among said branch ducts from said principal duct in accordance with the control desired, said means comprising a thermostatically controlled damper element mounted in said principal duct at the point where said temperature regulating medium enters said branch ducts from said main duct, said element being adapted to swing between two extreme positions, in each of which positions, said damper will substantially close the opening to one of said branch ducts.

4. Means for stabilizing the natural frequency of oscillation of an electric circuit having capacity and inductance of substantial magnitude and sufficient to give said circuit a natural period of electrical oscillation, said means comprising a chamber for receiving the elements of said electrical circuit, said chamber having walls of material having heat' conductivity of the order of metals, means for producing a'relatively rapid flow of a fluid medium through said chamber in contact with said electrical circuit elements, means for supplying heat to said 'fluid medium, and means responsive to temperature changes of said fluid medium immediately after it has made contact with said electrical circuit elements for varying the amount of heat supplied to said fluid medium by said heat supplying means.

5. Means for stabilizing the operation of an oscillation generator or similar apparatus where'- in heat is developed during operation sufiicient to alter its operating characteristics, said means comprising a chamber having walls of material having heat-conductivity of the order of metals for receiving the apparatus to be stabilized, means for producing a flow of a fluid medium in heatdissipative relation to said apparatus and said Walls, means for supplying heat to said fluid medium at a rate sufficient to maintain the temperature of said fluid medium above that of ambient temperature and means responsive to temperature changes in said medium for varying the amount of heat supplied to said fluid medium by said heat supplying means.

6. Means for stabilizing the operation of an oscillation generator or similar apparatus wherein heat is developed during operation suflicient to alter itsoperating characteristics,said means comprising a chamber having walls of material having heat-conductivity of the order of metals for receiving the apparatus to be stabilized, said chamber having an inlet and outlet located in oppositely disposed walls of said chamber, a duct connecting said inlet and outlet externally of said chamber, means for producing a circulating flow of a fluid medium through said duct and chamber, and in heat-dissipative relation to said apparatus and Walls, means located in the path of flow of said fluid medium for supplying heat to said fluid medium and a thermostat supported in said chamber at said outlet and responsive to temperature changes Within said medium for controlling the amount of heat supplied to said fluid medium by said heat supplying means.

7. Means for stabilizing the operation of an oscillation generator or similar apparatus having frequency determining components wherein heat is developed during operation suflicient to alter its frequency characteristics, said means comprising a chamber for receiving the frequency determining components of said generator, saidchamber having Walls of material having heat-conductivity of the order of metals, means for producing a flow of a fluidmedium through said chamber in one direction only in heat-dissipative relation to said components and said walls, means for supplying heat to said fluid medium and means responsive to temperature changes in said medium for varying the amount of heat supplied to said fluid medium by said heat supplying means. a

8. Means for stabilizing the operation of an oscillation generator or similar apparatus having frequency determining'components wherein heat is developed during operation sufficient to'alter its frequency characteristics, said means comprising a chamber having walls of material having heat-conductivity of theorder of metals for receiving the apparatus to be stabilized, said chamber having an opening in opposite walls, a duct connecting said openings externally of said chamber to constitute a closed circulatory path, means for producing a circulating flow of a fluid medium through said duct and chamber, and in heat-dissipative relation to said apparatus and Walls, means for supplying heat to said fluid medium prior to its entering said chamber and means responsive to temperature changes of said fluid medium passed through said chamber for controlling the amount of heat supplied to said fluid medium by said heat supplying means prior to its re-entering said chamber.

9. Means for stabilizing the natural frequency of oscillation of an electric circuit having frequency determining components including capacity and inductance of substantial magnitude and sufficient to give said circuit a natural period of electrical oscillation, at least one of said inductance and capacity being variable, said means comprising a chamber for housing said components, the walls of said chamber having heat conductivity of the order of metals, means vfor producing a relatively rapid flow of a fluid immediately after it has 

